The present invention relates to a material for packaging light-sensitive materials, particularly to one having improved properties such as high physical strength, high degree of light-rightness, ease of bag making and high degree of flatness.
Various materials are currently used for the purpose of packaging light-sensitive materials and typical examples are listed below: films made by blending linear low-density polyethylene (L-LDPE) and low-density polyethylene containing light-shielding materials; two uniaxially drawn films which are superposed in such a way that the drawing direction of one film forms an angle of 30.degree.-90.degree. with that of the other film, with the resulting assembly being laminated with low-density polyethylene on the surface of one side (see Examined Japanese Utility Model Publication No. 56-19087); two uniaxially drawn films of linear low-density polyethylene containing a light-shielding material are superposed in such a way that the drawing direction of one film forms an angle of 30.degree.-90.degree. with that of the other film as described in JP-A-63-121048 (the term "JP-A" as used hereinafter means an "unexamined published Japanese patent application"); and multi-layer coextruded films containing a light-shielding material as described in JP-A-62-18548, JP-A-62-43356, JP-A-62-104247, JP-A-63-1540, JP-A-63-1541, and JP-A-63-53547.
However, these and other prior art materials for packaging light-sensitive materials are not completely satisfactory in that they do not meet all the requirements for such packaging materials. For instance, some of the conventional products lack strength which is one of the most important properties for packaging materials. In order to insure strength, some products have an increased film thickness, but bags cannot be easily made from these products. Other products insure strength by lamination but then the number of steps involved increases making economical production difficult. Yet other products lose light-shielding property when pinholes develop, or they have a low degree of flatness, or their production rate is low on account of the difficulty involved in low-temperature sealing. Under these circumstances, it has been desired to develop an improved material for packaging light-sensitive materials that meet all the requirements for such packaging materials.